solarcarfandomcom-20200216-history
Electrical Systems
Motors Most teams use high efficiency wheel-mounted DC brushless motors. Many American teams use NGM's SCM150 motor. NGM can be difficult to contact, but is still alive as NuGen Motors. Many teams are switching from NGM motors to the CSIRO motor kit, so you may be able to purchase one of these motors second-hand. A CSIRO motor is popular amongst teams at the World Solar Challenge, but takes a large amount of time to construct since you are responsible for designing the majority of the motor. The winning team Tokai had a custom motor constructed by Mitsuba , and some of their motors are standard for use in Japanese solar car races. Motor Controllers Many teams use the NGM motor controllers (EVC402-042/092 series) or the Tritium motor controllers . The NGM motor controller is somewhat infamous for having strange shutdowns and errors, and the company is essentially defunct so offers no real support. By contrast, the Tritium motor controllers have decent support and recently released a new model Wavesculptor 22. Some teams have claimed that the Tritiums suffered from lower efficiency than the NGM motor controller. The new model is smaller and more efficient, so this may no longer be as big of an issue. Teams with expertise in power electronics may even attempt to create their own motor controllers, as Stanford is doing. Batteries Deciding on a specific battery technology may depend largely on the particular race regulations limiting the allowed weights of different battery technologies. The main factors are the energy to weight ratios of a specific battery, monetary cost, and the allowed number of batteries. Sealed Pb-acid batteries are inexpensive, but generally considered too heavy for competitive use. You should look into the various advantages of NiMH, LiFePO4, Li-ion, and Li-Polymer technologies. While each car is required to have a battery protection system, the relative stability of each battery type may be an additional factor in determining which battery to use on your car. Battery Protection Systems Depending on a team's specialty there are a wide variety of custom and off-the-shelf battery monitoring systems. Solar Array Since solar car arrays are limited by space, the efficiency of the array is an important attribute. Two types of solar cells are currently plausible for competitive solar car racing: Monocrystalline Silicon Cells and Multijunction Solar Cells. Silicon Cells achieve efficiencies of about 22%, and an array can cost about $20,000. Multijunction cells may reach about 30% efficiency but may cost 10 times as much. From this cost difference there is a clear divide in the two classes of solar car teams. SunPower cells are generally considered the most efficient amongst silicon cells, although some teams have been competitive with other companies' technology. Sanyo HIT cells now pose an alternative, used by Tokai in the World Solar Challenge. Power Trackers Maximum Power Point trackers find the ideal operating voltage of the solar cells to maximize power output. This power is then converted to match the voltage of the batteries. MPPTs operate at high efficiencies around 95%. Drivetek Power Trackers (from the Biel School of Engineering) have been popular, and some teams attempt to make their own power trackers. Teams which have been succesful with their power tracker designs often go on to sell their trackers to other teams. This is where most tech used in solar teams originates. System Integration *The UC Berkeley team uses an modified Arduino (dubbed the "Brain") that can plug into function specific skeleton boards. http://calsolbrain.googlecode.com